TAUVEX - A wide field UV imager

TAUVEX is a small UV imager payload originally designed to fly on a mid-sized satellite and perform a UV sky survey, but later adopted as one of the scientific instruments on the Spectrum X-Gamma (SRG) mission. Its size, mass, and power budget make it of interest to small missions for performing UV observations. Within its minuscule resource budget we managed to include three 20 cm telescopes which image the same 0.9 degree field with 10″ or better resolution. The sensitivity on stellar objects is m_UV ≈20 (5 σ) with one to a few hours exposure. The experiment contains significant redundancy at component and system level in addition to the inherent redundancy of three co-aligned telescopes. The design of TAUVEX optimized not only the on-orbit reliability but also extremely low weight (total mass is 33 kg) and low power consumption (64W or less for operating and maintaining the proper thermal regime). In addition to its scientific tasks, TAUVEX provides the aspect solution for the SODART X-ray telescopes on SRG and supplies SRG with fine stabilization signals. The TAUVEX experiment has been qualified and its performance is as predicted by modeling the design. The flight model has been assembled and will begin its burn-it and calibration in winter 1997. We expect TAUVEX to be ready to fly in early 1998. Its operation on board SRG for the nominal three-year duration of the mission will yield catalogs of tens of thousands of UV-selected AGNs, hundreds of thousands of galaxies, and about one million stars, all measured in three simultaneous UV spectral bands. In addition, some thousands of sources will be studied for photometric variability on time scales of 10 msec up to hours, and longer for cases of revisits. All this, in addition to the unique science done in conjunction with the high-energy imagers on board SRG.